Abstract

Final report on Contract No 7210-PR/057, 1 July 1997 to 31 December 2000.

The aim of this research project is to characterise and optimise the forming and joining behaviour of high-strength cold rolled steels by application of different post-treatments. BH, isotropic, IF-HS, DP and TRIP steel grades, electrogalvanised ZE, hot-dip galvanised Z, and galvannealed ZF have been investigated. As post-treatment systems prelubes, prephosphating and organic preprimers have been applied. The tribological tests on the strip drawing facility indicated that generally the friction could be minimised by means of prelubes. The phosphated and the thin film organic coated material variants were shown to be more formable than the metallic-coated materials without post-treatments. The positive influence of these post-treatments is stronger for high-strength materials. The springback behaviour tests indicate the importance of the draw-bead usage and the blank holder force for the result of forming operations. The deflection of the car outer door panel is attributable to the sheet thickness. However, the dynamic denting resistance depends on sheet thickness and the strength of the material. Generally, the electrode lifetime in spot welding operations is shortened by post-treatments. The experience of the project shows the potential of cooperation with a joining system provider in mechanical joining techniques. The tooling and the joining element can be mostly adjusted to the joined materials and the joining function.